1. Field of the Invention
The present invention relates generally to an optical fiber distribution enclosure for use in a passive optical network (PON), and more particularly, to a high density optical fiber distribution enclosure for splitting an optical signal carried on an optical fiber of a feeder cable into multiple optical signals carried on a plurality of optical fibers of a distribution cable in the outside plant of a PON.
2. Technical Background
It is now well known to use an optical splitter or splitter module (sometimes also referred to as a coupler module) in the outside plant of a passive optical network (PON) to distribute a broadband optical communications signal from a service provider to multiple subscribers. In a typical PON, an optical fiber distribution enclosure, sometimes referred to as a fiber distribution hub (FDH), a fiber distribution terminal (FDT) or a local convergence cabinet (LCC), is positioned at a convenient location along a primary feeder cable to split the optical signal carried on an optical fiber of the feeder cable into multiple optical signals carried on a plurality of optical fibers of one or more distribution cables. An outdoor cabinet for interconnecting an optical fiber of a feeder cable with at least two optical fibers of a distribution cable at a local convergence point beyond the central office in a PON is shown and described in U.S. Pat. No. 6,792,191 assigned to Corning Cable Systems LLC of Hickory, N.C.
In the LLC described in the '191 patent, the feeder cable and the distribution cable are first routed into the cabinet and optical fibers of the feeder cable and the distribution cable are then spliced to a relatively short length of optical fiber having a connectorized end, referred to in the art as a “pigtail.” Each pigtail of the feeder cable is then routed to an input fiber adapter provided on a coupler module mounted within the cabinet. Likewise, the pigtails of the distribution cable are routed to output fiber adapters provided on the coupler module. In this manner, the optical signal carried on an optical fiber of the feeder cable is split (i.e., divided) into multiple optical signals carried on different optical fibers of the distribution cable. In a particular example, eighteen (18) optical fibers of a feeder cable are each split into sixteen (16) optical fibers of a distribution cable utilizing 1×16 coupler modules. In another particular example, nine (9) optical fibers of a feeder cable are each split into thirty-two (32) optical fibers of a distribution cable utilizing 1×32 coupler modules. In either case, the corresponding optical fiber distribution cabinet is referred to as a “288-Fiber Capacity Fiber Distribution Hub (FDH)” because the optical connections between the feeder cable and the distribution cable(s) result in a maximum of 288 distribution cable optical fibers. While a 288-Fiber Capacity FDH is common, a cabinet resulting in any convenient number of distribution cable optical fibers is also possible, including for example, 144, 432, 576, etc.
Regardless of the number of optical connections, the optical fiber distribution enclosure functions as an interface between the service provider's optical network (e.g., the PON) and the optical fibers connecting the individual subscribers to the network. The enclosure ensures mechanical and environmental protection for the optical fibers, the optical connections, and the optical hardware and equipment located inside the cabinet, while at the same time providing convenient access to the optical connections for the service provider to establish or reconfigure service to the subscribers. In addition, the enclosure provides an organized routing and management system for the optical fibers, as well a point of access to verify the operation and integrity of the optical network. While existing enclosures (including the LLC described in the '191 patent) satisfy at least some of the above objectives, all function less than optimally in one or more of the desired attributes. In particular, none of the existing enclosures is configured to interconnect optical fibers of a pre-connectorized feeder cable stub with optical fibers of a pre-connectorized distribution cable stub in an outside plant enclosure with organized cable routing and management and easy and ready access to the optical connections between the connectorized optical fibers of the distribution cable and connectorized output optical fibers from a splitter module.
Furthermore, existing optical fiber distribution enclosures are typically suspended from a utility pole or mounted on a utility pad along a street of a neighborhood. The current demand, or the planned expansion, of the optical network requires the size of the distribution enclosure to be significantly reduced in order to at least maintain the existing aesthetics (sometimes referred to as “curb appeal”). At the same time, many new deployments of optical networks require the distribution enclosure to be buried underground for improved aesthetics. Obviously, the need for increased density of optical connections and the desire for at least similar or improved aesthetics are inherently at odds with one another. Accordingly, what is needed is a high density optical fiber distribution enclosure configured to interconnect a pre-connectorized optical fiber of a feeder cable with a plurality of pre-connectorized optical fibers of a distribution cable in a compact housing. What is further needed is such a distribution enclosure that also facilitates handling, installation, initial configuration, reconfiguration and testing, and which is scalable to accommodate an increasing number of optical connections as service is provided to additional subscribers. In particular, an optical fiber distribution enclosure is desired for a buried optical network to provide centralized splitting in a high density, environmentally sealed closure. As will be described in further detail hereinafter, the present invention provides these and other features and advantages, and thereby satisfies the heretofore unresolved need for a high density optical fiber distribution enclosure.